How can you sync Blender configs between multiple machines?
Yes, this is in fact possible: 

This is part of the Blender Cloud functionality is called Blender Sync.
And guess what: it is completely free! 

This will sync your Blender Startup and User Preferences to the Blender Cloud and you can then retrieve it from any new install. It works even cross plattform (I use it on Linux and Windows)

First, create a blender ID here: 
https://www.blender.org/id/

Then download the blender Cloud addon and install it:
https://cloud.blender.org/services

Then log in via the addon and bingo, your settings will be synced up to the cloud. 

See here for all the details:
https://cloud.blender.org/blog/introducing-blender-sync

I have noticed that some people have heard of this before, but assumed that it was only part of the paid Blender Cloud. But it is in fact free. I hope this will boost your productivity and make sure you can save time only having to configure Blender once.